title: ADHD and the externalizing spectrum: direct comparison of categorical, continuous, and hybrid models of liability in a nationally representative sample.
abstract: OBJECTIVE
  Alcohol use disorders, substance use disorders, and antisocial personality disorder share a common externalizing liability, which may also include attention-deficit hyperactivity disorder (ADHD). However, few studies have compared formal quantitative models of externalizing liability, with the aim of delineating the categorical and/or continuous nature of this liability in the community. This study compares categorical, continuous, and hybrid models of externalizing liability.
  
  
  METHODS
  Data were derived from the 2004-2005 National Epidemiologic Survey on Alcohol and Related Conditions (N = 34,653). Seven disorders were modeled: childhood ADHD and lifetime diagnoses of antisocial personality disorder (ASPD), nicotine dependence, alcohol dependence, marijuana dependence, cocaine dependence, and other substance dependence.
  
  
  RESULTS
  The continuous latent trait model provided the best fit to the data. Measurement invariance analyses supported the fit of the model across genders, with females displaying a significantly lower probability of experiencing externalizing disorders. Cocaine dependence, marijuana dependence, other substance dependence, alcohol dependence, ASPD, nicotine dependence, and ADHD provided the greatest information, respectively, about the underlying externalizing continuum.
  
  
  CONCLUSIONS
  Liability to externalizing disorders is continuous and dimensional in severity. The findings have important implications for the organizational structure of externalizing psychopathology in psychiatric nomenclatures.
authors.affiliation: National Drug and Alcohol Research Centre, University of New South Wales, Sydney, NSW, 2052, Australia, n.carragher@unsw.edu.au.
authors.forename: Natacha
authors.initials: N
authors.lastname: Carragher
authors.forename: Robert F
authors.initials: RF
authors.lastname: Krueger
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Eaton
authors.forename: Kristian E
authors.initials: KE
authors.lastname: Markon
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Keyes
authors.forename: Carlos
authors.initials: C
authors.lastname: Blanco
authors.forename: Tulshi D
authors.initials: TD
authors.lastname: Saha
authors.forename: Deborah S
authors.initials: DS
authors.lastname: Hasin
mesh_terms: D000293:Adolescent; D000328:Adult; D000987:Antisocial Personality Disorder / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology* / Q000523:psychology; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis; D005260:Female; D006801:Humans; D007389:Internal-External Control; D016015:Logistic Models; D008297:Male; D008960:Models, Psychological; D015233:Models, Statistical; D011336:Probability; D011599:Psychopathology; D012720:Severity of Illness Index; D019966:Substance-Related Disorders / Q000175:diagnosis* / Q000453:epidemiology* / Q000523:psychology; D014029:Tobacco Use Disorder / Q000453:epidemiology